Mycobacterium kansasii is one of the most common cause of pulmonary diseases due to nontuberculous mycobacteria. We investigated the changing in the number of isolation of M. kansasii and the clinical characteristics of M. kansasii pulmonary disease in Korea. Through searching the database of the Korean Institute of Tuberculosis, we identified the cases of isolated M. kansasii from 1992 to 2002. The number of M. kansasii isolation had increased from once in 1992 to 62 in 2002. Fifteen patients with M. kansasii pulmonary disease were identified during the period January 1997 to December 2002. Twelve patients (80%) were male and fourteen (93%) were from highly industrialized areas. The most common symptom was a cough. Seven patients (47%) had a cavitary lesion and right upper lobe was most commonly involved. Patients responded well to isoniazid and rifampicin based regimens both bacteriologically and radiographically. In conclusion, M. kansasii isolation has increased, especially in highly industrialized areas, as well as other nontuberculous mycobacteria in Korea.